(1) Field of the Invention
The present invention pertains to an apparatus that is one part of a conveying system for transferring objects, such as bottles, where the apparatus removes layers of the objects from a pallet or, in reverse operation, arranges the objects in layers on a pallet. In particular, the present invention pertains to an apparatus that may be employed to depalletize objects or to palletize objects, where in the depalletizing mode of operation the apparatus has a slipsheet retainer that holds a slipsheet below a layer of objects being depalletized from the stacked layers of objects and prevents the slipsheet from moving with the layer of objects as the layer of objects is depalletized.
(2) Description of the Related Art
Many containers such as bottles, cans, jars, jugs, etc. are packaged on pallets for transportation from a manufacturer to a user of the container or object. The pallet loads often include layers of the objects, each separated by a paperboard slipsheet, stacked on top of a pallet constructed of wood. The layers of objects and the slipsheets on which the layers rest are secured on the top surface of the pallet by banding, plastic sheet wrap or by other equivalent methods. The pallet loads facilitate the transportation of a significant number of the objects on each pallet load from the manufacture of the objects, through distribution and ultimately to the end user of the objects.
Upon receipt of a pallet load of objects the user of the objects removes the banding or sheet wrap that secured the objects to the top surface of the pallet and then must unload the pallet by removing the topmost layer of objects on the pallet load, removing the slipsheet that supported the topmost layer, then removing the next lower layer of objects from the pallet load and its slipsheet until the pallet is completely unloaded. In many conveyor systems in which objects are unloaded from pallet loads and/or are loaded onto pallets, the faster the system can operate to unload and/or load pallets the more cost efficient is its operation. With manual unloading and loading of pallets being long recognized as slow and expensive, a number of different types of machines have been developed over time that quickly perform the function of unloading and/or loading pallets. These machines are referred to as depalletizers and/or palletizers in the conveying industry. Examples of these types of machines are described in U.S. Pat. Nos. 2,774,489, 3,780,884; 3,844,422; 3,954,190; 3,974,922; 4,058,225; 4,197,046; 4,214,848, and 4,557,656 the disclosures of all of which are incorporated herein by reference.
FIG. 1 is a schematic representation depicting a depalletizer, palletizer apparatus that comprises many features found in other prior art apparatus. The machine shown in FIG. 1 includes an object infeed section A, an elevator section B, and an object outfeed section C. As stated earlier, machines of this type are known in the prior art and various examples of these machines are disclosed in the above-listed patents. In order to simplify the explanation of the construction and operation of these types of machines the drawing of the machine in FIG. 1 has been simplified, deleting many of the intricate component parts of the machine, examples of which are disclosed in the above-listed patents, that enable the machine to function in the manner to be described. The machine will be described as depalletizing and palletizing objects, in this case plastic blow-molded bottles as shown in FIG. 1. It should be understood that "objects" is intended to mean any of the various different types of objects that may be transported in pallet loads and is not intended that the interpretation be limited to plastic bottles.
The sections of the machine shown in FIG. 1 are all supported by a framework 10. At the object infeed section A, the framework supports the end of a conveyor depicted as a belt and pulley conveyor 12. However, any other type of known conveyor may be employed to transport pallets of objects to the machine infeed section A. As shown in FIG. 1, the infeed conveyor 12 has transported a pallet load into the object infeed section A. The pallet load is comprised of several layers of objects 14, in this example plastic bottles, that are each separated from each other by a paperboard slipsheet 16 positioned under each layer of objects 14. The layers of objects 14 and the slipsheets 16 are all supported on a pallet 18, for example a wooden pallet although pallets are constructed of other types of materials. As shown in FIG. 1, the banding or plastic sheetwrap that usually secures the layers of objects 14 and slipsheets 16 to the top surface of the pallet 18 has been removed. With the pallet load of objects 14 positioned by the infeed conveyor 12 in the object infeed section A, the control system of the machine has precisely positioned the pallet load relative to the sections of the machine to permit the quick depalletizing of each layer of objects in the pallet load. The direction of movement of the infeed conveyor 12 may be reversed for operation in a palletizing mode.
Shown at the top of the object infeed section A is a sweeper mechanism 22. The sweeper mechanism 22 has a generally rectangular base 24 at its top that is supported in the machine to move horizontally across the length of the machine between the object infeed section A and the object outfeed section C, and also to move vertically in the elevator section B as will be explained. Suspended from four edges of the base 24 are four side plates 26, only three of which are visible in FIG. 1, that are suspended from the four edges of the base 24. A pivot rod supports each of the side plates 26 from each edge of the base 24 for relative pivoting movement of the side plates 26 to the base 24 as represented by the arrows in FIG. 1. The pivoting movement of the side plates 26 is controlled by pneumatic actuators that can be controlled to pivot the side plates 26 upwardly to positions that are substantially horizontal and parallel with the base 24.
A gripper mechanism 28 is also supported by the frame in the object infeed section A of the machine. The gripper mechanism 28 is supported by the frame for vertical movement of the mechanism across the entire vertical height of the object infeed section A. The gripper mechanism 28 comprises a pair of jaws 32 that are controlled to close and grip the back edge of a slipsheet 16 in depalletizing operation of the machine as will be explained.
An elevator mechanism 34 is supported in the elevator section B of the machine. The elevator mechanism 34 is supported for vertical movement across the vertical height of the elevator section B. The elevator mechanism 34 has a smooth, flat top sliding surface 36 that is controlled by the control system of the machine to be selectively positioned by the elevator mechanism adjacent the tiers of slipsheets 16 and the top surface of the outfeed conveyor to be described. In some prior art machines of this type the elevator mechanism 34, the sweeper mechanism 22 and the gripper mechanism 28 are all part of the same unit and move together vertically. However, these mechanisms can also be made to move independently of each other.
An end of an outfeed conveyor 38 is supported in the machine frame in the object outfeed section C. The outfeed conveyor 38 is depicted as a belt and pulley conveyor but may be any other type of conveyor. As with the infeed conveyor 12, the conveying direction of the outfeed conveyor 38 may be reversed in order to employ the machine in both a depalletizing mode and a palletizing mode.
The operation of the representative depiction of the prior art depalletizer/palletizer shown in FIG. 1 is similar to the operation of most prior art palletizer/depalletizers. In the depalletizing mode of operation, a pallet load consisting of a pallet 18 having layers of objects 14 arranged thereon with each layer separated by a slipsheet 16 is transported by the infeed conveyor 12 in a downstream direction until the pallet load is in its proper position in the object infeed section A as shown in FIG. 1. The positioning of the pallet load in the object infeed section is controlled by sensors so that the layers of objects 14 and their slipsheets 16 are in desired positions relative to the elevator section B and the gripper mechanism 28. If the sweeper mechanism 22 is positioned in the object infeed section A as the pallet load is conveyed to this section it must be moved completely to the top of the infeed section A in the position shown in FIG. 1 and at least the one side plate 26 shown at the right of the sweeper mechanism 22 in FIG. 1 must be raised to provide clearance inside the remaining three depending side plates 26 of the sweeper mechanism to receive the topmost layer 42 of objects on the pallet load. If the sweeper mechanism 22 is positioned in the elevator section B or the object outfeed section C, it is first raised to its topmost position and then the same side plate 26 facing the pallet load is raised. The sweeper mechanism is then moved horizontally over the topmost layer 42 of objects to its position shown in FIG. 1. With the sweeper mechanism 22 positioned over the topmost layer 42 of objects, the side plates 26 are moved to their downwardly depending position where their interior, mutually opposed surfaces come into contact around the grouping of objects 14 in the topmost layer 42. Also, prior to insertion of the pallet load in the object infeed section A by the infeed conveyor 12, the gripper mechanism 28 must be raised to the top of the object infeed section A where it will be high enough to clear the topmost layer of objects 42 of the pallet load as they are moved into the object infeed section.
Next, the elevator mechanism 34 is raised so that the sliding surface 36 is adjacent the topmost slipsheet 44 as shown in FIG. 1. With the sliding surface 36 of the elevator mechanism 34 adjacent the topmost slipsheet layer 44, the gripper mechanism 24 is lowered from its position at the top of the object infeed section until it also is adjacent the topmost slipsheet layer 44 on the opposite side of the elevator mechanism sliding surface 36 as shown in FIG. 1. The jaws 32 of the gripper mechanism 28 are then operated to clamp along the rearward edge of the topmost slipsheet layer 44 as shown in FIG. 1.
With the jaws 32 of the gripper mechanism 28 holding the rearward end of the topmost slipsheet layer 44, the sweeper mechanism 22, with its side plates 26 all depending downwardly, next moves to the left as shown in FIG. 1. This motion of the sweeper mechanism 22 slides all of the objects in the topmost layer 42 to the left sweeping the objects off of the topmost slipsheet 44 held by the gripper mechanism 28 and onto the top sliding surface 36 of the elevator mechanism 34. This horizontal movement of the sweeper mechanism 22 is controlled to position all of the objects in the topmost layer 42 on the elevator mechanism sliding surface 36, and then the horizontal movement of the sweeper mechanism 22 is stopped by the control system of the machine.
With the topmost layer of objects 42 positioned on the sliding surface 36 of the elevator mechanism 34, the gripper mechanism 28 is disengaged and the elevator mechanism then moves vertically downward. As the elevator mechanism moves vertically downward the sweeper mechanism 22 is controlled to travel with the elevator thereby holding the topmost layer of objects 42 in a group on the sliding surface 36 of the elevator mechanism. The downward movement of both the elevator mechanism and the sweeper mechanism continues until the sliding surface 36 of the elevator mechanism is positioned adjacent the outfeed conveyor 38.
With the sliding surface 36 of the elevator mechanism positioned adjacent the outfeed conveyor 38, the sweeper mechanism 22 then moves horizontally to the left as shown in FIG. 1, sweeping the topmost layer of objects 42 onto the outfeed conveyor 38. At this point in its operation, the outfeed conveyor 38 is not activated or operates for a short time as the sweeper mechanism 22 sweeps the topmost layer of objects 42 onto the stationary outfeed conveyor 38. The sweeper mechanism is controlled to position all of the objects of the topmost layer on the outfeed conveyor, and then to raise vertically to the top of the object outfeed section C. The sweeper mechanism 22 then moves horizontally to the right as viewed in FIG. 1 across the elevator section B to the top of the object infeed section A. Simultaneously with this movement of the sweeper mechanism 22, the elevator mechanism 34 raises in the elevator section B until the sliding surface 36 of the mechanism is positioned adjacent the next lower slipsheet 46 of the pallet load. With the elevator mechanism in place adjacent the next lower slipsheet 46, the sweeper mechanism 22 moves downwardly in the object infeed section A to a position where the base 24 of the mechanism is just above the next lower layer of objects 48 and its side plates 26 surround all of the objects in this layer. The gripper mechanism 28 also moves downward and grips the next slipsheet 46. The sweeper mechanism 22 then moves to the left in the same manner as described earlier to sweep off the next lower layer of objects 48 together with the slipsheet 44 on top of the layer of objects onto the sliding surface 36 of the elevator mechanism. The process continues as described earlier until all of the layers of objects are swept off the pallet 18 and onto the outfeed conveyor 38. The slipsheets 16 left on top of the layer of objects that have been depalletized are later removed downstream in the conveyor system.
Alternatively, in the operation of prior art machines of this type, once the sweeper mechanism 22 has swept the layer of objects from the sliding surface of the elevator mechanism 34 onto the outfeed conveyor 38, both the elevator mechanism and sweep mechanism together move vertically upwardly in the elevator section with the elevator mechanism 34 being controlled to stop adjacent the next lower slipsheet 46 and the sweeper mechanism 22 moving to the top of the elevator section. The sweeper mechanism 22 then moves horizontally from the elevator section B to the object infeed section A and then vertically downward over the next lower layer of objects 38 to be swept out of the object infeed section off of the pallet load.
Also in the operation of prior art machines of this type, depending on the size of the objects being swept from the pallet load, it may be necessary for the control system of the machine to raise the side plates 26 of the sweeper mechanism 24 as it moves horizontally over the pallet load after the topmost layer of objects 42 has been swept from the pallet load.
It can be seen that when the last layer of objects 52 has been swept off the last slipsheet 54 and onto the elevator sliding surface 36, the object infeed section A of the machine is empty except for the presence of the pallet 18. In prior art machines of this type, there are various different types of mechanism that are employed to remove the pallet 18, for example a separate conveying system for the emptied pallet that would extend transverse to the flow path from the infeed conveyor 12 through the machine to the outfeed conveyor 38. With the pallet removed from the object infeed section A, this section of the machine is prepared to receive the next pallet load of objects, even while the sweeper mechanism 22 is sweeping the last layer of objects 52 across the elevator sliding surface 36 onto the outfeed conveyor 38. When the last layer of objects 52 is removed from the pallet the gripper mechanism 24, holding the last slipsheet 54 on the top surface of the pallet 18, releases the slipsheet so that both the pallet and slipsheet may be removed from the object infeed section A. However, at this time the gripper mechanism 28 is toward the bottom of the object infeed section A just above the infeed conveyor 12. The infeed conveyor 12 must then wait until the gripper mechanism 28 is raised up to the top of the object infeed section A so that the next pallet load of objects can be moved into the object infeed section on the infeed conveyor 12. This movement of the gripper mechanism 28 out of the path of pallet loads on the infeed conveyor 12 delays the time in which the next pallet load can be moved into the object infeed section and the depalletizing of this pallet load can commence. With machines of this type being more cost efficient by depalletizing layers of objects from a pallet load as quickly as possible, any delay in the depalletizing operation such as that caused by the repositioning of the gripper mechanism 28 back to the top of the object infeed section A lowers output efficiency and thereby increases the cost of operating the conveyor system.